Defoliation‐induced compensatory transpiration is compromised in SUT4‐RNAi Populus

Abstract

Sucrose and its hexose breakdown products contribute significantly to the high osmolalities often found in leaves of temperate latitude tree species including Populus (Rennie & Turgeon, 2009; Slewinski, Zhang, & Turgeon, 2013). High osmolality in the mesophyll supports leaf turgor in trees, and is also thought to reflect the operation of a subcellular partitioning mechanism that effectively concentrates

Perturbation of tonoplast sucrose transport alters carbohydrate utilization for seasonal growth and defense metabolism in coppiced poplar

“…According to multiple studies involving temperate tree species, transcript levels for SUT4 encoding the tonoplast sucrose transporter peak in the winter in both stem and apical buds (Figure S3) (Dobbelstein et al 2018; Ko et al 2011; Sreedasyam et al 2023). Partial or full loss of SUT4 function in Populus has been associated with compromised carbohydrate metabolism, turgor and osmotic responses to drought (Frost et al 2012; Harding et al 2020; Harding et al 2022). Given the association of desiccation and altered turgor with winter freezing, we propose in light of our findings under warm versus cool growing conditions that SUT4-mediated sucrose trafficking within stems has anticipatory roles in winter fitness, irrespective of the occurrence of ice crystal formation.…”

“…Turgor control may also be considered as a contributing factor to the relative improvement in sut4 sprout growth under summer conditions. Turgor of fully expanded leaves is greater in sut4 than control plants because of higher sugar osmolyte levels (Harding et al 2020; Harding et al 2022). This implicates a role for SUT4 in modulating early expansion growth in control plants where SUT4 expression increases as leaves transition from sink to source organs (Payyavula et al 2011).…”

“…In addition, SUT4 is expressed in overwintering sink organs of several temperate tree species including Populus (Dobbelstein et al, 2018, Ko et al, 2011, and its expression varies in accordance with abiotic stress (Xu et al, 2017, Payyavula et al, 2011, Frost et al, 2012, Harding et al, 2022. Effects of SUT4 silencing or knockout (KO) on source leaf turgor control and starch homeostasis have also been reported (Harding et al, 2020, Harding et al, 2022.…”

“…SUT4 gene expression varies with a range of abiotic stresses including light, temperature, and drought (Xu et al 2017). Effects of SUT4 impairment on turgor, osmotic adjustment, growth, and antioxidant metabolism in leaves of poplar suggest the potential for SUT4 to impact many homeostatic processes through sensing-signaling pathways that remain to be elucidated (Frost et al 2012; Harding et al 2020; Harding et al 2022). Notably, SUT4 -knockout (KO) impacts starch homeostasis, which suggests the potential for a conditional role of SUT4 in integrating utilization of the two major carbohydrate storage forms in Populus (Harding et al 2022).…”

Genome-wide analysis and characterization of Dendrocalamus farinosus SUT gene family reveal DfSUT4 involvement in sucrose transportation in plants

“…OsSUT2 promotes photosynthesis and sucrose distribution in plants under drought and salt stress (Ibraheem et al, 2011). PtaSUT4 transporters also function in photosynthesis (Frost et al, 2012) and drought response (Harding et al, 2020). Furthermore, PaSUT and OsSUT1 transporters are associated with phytohormone (auxin and cytokinin) signaling pathways in the translocation of sucrose in Petunia axillaris flower (Rolland et al, 2002;Iftikhar et al, 2020) and rice seeds (Zhao et al, 2022), respectively.…”